1. Technical Field
The present invention relates to a toner cartridge for feeding toner to electrophotographic recorders and the like.
2. Background Technology
Cylindrical toner cartridges have been known as conventional toner cartridges. A cartridge of this type is composed of an outer cylinder, an inner cylinder which rotatively contacts the inner surface of the outer cylinder and a pair of caps attached to opposite ends of the inner cylinder. The inner cylinder has an empty space therein to accommodate toner. A plurality of toner discharge outlets are defined in the side surface of the outer cylinder in the longitudinal direction thereof, while a plurality of toner discharge outlets also are defined in the side surface of the inner cylinder. The caps also are in contact with opposite ends of the outer cylinder, one of the caps having a toner filling opening which is usually equipped with a pug.
A method of filling toner in the toner cartridge set forth above will be described hereinafter. Firstly, the inner cylinder is rotated or turned relative to the outer cylinder so that the toner discharge outlets of the inner cylinder will not overlap the toner discharge outlets of the outer cylinder. Then the plug is removed from the toner filling opening and toner is filled into the toner cartridge. Thereafter the plug is put in the toner filling opening.
In order to feed the toner to an electrophotographic recorder using the toner cartridge which is filled with toner in the manner described above, the toner cartridge is attached to the electrophotographic recorder at a predetermined position thereof with the outer toner discharge outlets directed downwardly. Thereafter the inner cylinder is turned by a driving means so as to overlap the inner toner outlets with the outer toner outlets. As a result, the toner is fed to the electrophotographic recorder through the aligned and overlapped inner and outer toner discharge outlets.
The toner cartridge set forth above, however, has the following disadvantages. It is difficult to manufacture the inner and outer cylinders in a manner such that the inner cylinder contacts an inner surface of the outer cylinder and at the same time is rotatable with respect to the outer cylinder. When the outer diameter of the inner cylinder is manufactured to be less than the inner diameter of the outer cylinder, a gap is defined between the inner and outer cylinders. Such gap causes leakage therethrough of the toner. When the outer diameter of the inner cylinder is manufactured with high accuracy so as to conform to the inner diameter of the outer cylinder to prevent such leakage of the toner, the yield of the operation of manufacturing the inner cylinder is decreased, thereby increasing the cost of manufacturing the cartridge.
Previously proposed was a method of providing a cutaway portion at a part of the outer cylinder for facilitating the sliding motion of the inner cylinder when the outer diameter of the inner cylinder is manufactured to be the same as the inner diameter of the outer cylinder (Japanese Patent Application No. 1-122439). The cutaway portion is formed in the outer cylinder extending axially from opposite ends thereof but at positions where it does not overlap the toner discharge outlets of the outer and inner cylinders. Such cutaway portion, however, does not sufficiently reduce sliding friction between the outer and inner cylinders so that the turning of the inner cylinder remains difficult.